A. Field of the Invention
The embodiments of the present invention relate to a method for treating hearing loss, and more particularly, the embodiments of the present invention relate to a method for treating sensorineural hearing loss due to various causes by using donepezil hydrochloride (ARICEPT®).
B. Description of the Prior Art
Hearing loss is an insidious handicap that has no social barriers. The limitations imposed by the condition often are not tolerated and are poorly understood.
Hearing impairment affects up to 30% of the international community and an estimated 70 million people are deaf in the world. Sensorineural hearing loss appears to occur twice as often in developed countries in comparison to underdeveloped countries. 1.2 out of 1000 children have bilateral sensorineural hearing loss of at least 50 decibels.
Twenty-one million people in the U.S. are estimated to be hearing impaired, including approximately 1% who are deaf. An estimated 4000 infants, who are hearing impaired and another 37,000 children with milder degrees of hearing loss, are born in the U.S. each year. Recent analysis suggests that up to 6 of every 1000 infants born will have some degree of hearing impairment.1 1 Barry Strasnik and Karen K. Hoffman. Inner Ear, Genetic Sensorineural Hearing Loss. eMedicine.com, Inc. 2004.
The majority of the deaf patients are people with sensorineural hearing loss. The current treatment of such patients is ineffective. The only way for their social rehabilitation is audioprosthetics. Development of new methods of treatment and rehabilitation is required in order to offer comprehensive service to people with hearing loss and their families. Pediatricians, audiologists, neurologists, speech-language pathologists, educational specialists, and otolaringologists must share in the direction of these efforts.
Sensorineural hearing loss is caused by different pathological processes. It appears as a consequence of the damage to the internal ear, cochlea, external auditory hair cells, and other cochlear structures, such as the fibers of the auditory nerve as a result of ototoxic and infectious (bacterial and viral) impact, vascular disorders in the vertebrobasilar system with a damage to central and peripheral areas of cranial nerve VIII, craniocerebral trauma with basilar skull fractures and fractures of the pyramid of the temporal bone, tumors (neurinomas) of CN VIII, tumors of the cerebellopontine angle, etc.
A number of complications can arise prior to birth, during the birth process, or soon after birth causing hearing loss. These conditions for newborns include family history of hearing loss, congenital infections (e.g. rubella), craniofacial anomalies, low birth weight, hyperbilirubinemia, ototoxic medications, bacterial meningitis, severe depression at birth (Apgar scores=0-4 at 1 min; 0-6 at 5 min), prolonged medical ventilation, stigmata, or other findings associated with a syndrome known to include a sensorineural and/or conductive hearing loss.2 2 See Fred H. Bess and Larry E. Humes. Audiology. The Fundamentals. Williams &Wilkins, 1995; p. 184.
It is generally considered that nerve cells are not able to regenerate. But some researches including the applicant argue that under certain conditions nerve cells can be restored leading to a partial recovery of visual and auditory functions, which are interconnected.
25 years ago, applicant conducted a study of a small group of blind mute and deaf children (3 patients) at the age of 7-9 years old. There was an attempt to restore their visual function using galanthamine hydrobromide solution at the dosage of 0.1 ml of 0.5% of galanthamine hydrobromide for each year of life. The course of treatment included 15-20 injections. After the treatment was conducted, one of the patients manifested a minor improvement of auditory function. This finding gave an impetus to conduct additional research into the restoration of auditory function using acetylholinesterase inhibitors in conjunction with laser stimulation.
(1) Hyperbilirubinemia.
Hyperbilirubinemia is one of the high risk factors for developing sensorineural hearing loss. Hyperbilirubinemia is a very complex metabolic complication that is thought to result from the production of too much bilirubin or the inability of the system to clear the bilirubin from the blood by the liver. It occurs when the bilirubin concentration in the blood exceeds 6-8 mg/dl. Once this level is reached, the child's skin becomes yellowish, a condition sometimes referred to as jaundice.3 3 Id.
(2) Viral and Bacterial Diseases.
Severe viral and bacterial infections can result in varying degrees and patterns of sensorineural hearing loss. Infectious disease can be transmitted to the child by the mother in utero, a condition referred to as prenatal, congenital, or sometimes perinatal disease. A disease can also be acquired later in life, and is usually referred to as a postnatal condition. Many of prenatal diseases are considered a high-risk factor for hearing loss.
(3) Toxoplasmosis.
Toxoplasmosis is a disease caused by an organism (Toxoplasma gondii) that is transmitted to the child via the placenta. It is thought that the infection is contracted by eating uncooked meat or making contact with feces of cats. About 17% of infected newborns exhibit sensorineural hearing loss. The hearing loss is typically moderate and progressive.
Several postnatal infections produce sensorineural hearing loss. The cochlear damage produced by these viral or bacterial infections appears to be a result from the infecting agent entering the inner ear through the blood supply and nerve fibers.
(4) Sensorineural Hearing Loss Caused by Bacterial Meningitis.
Hearing loss is the most common consequence of acute meningitis. Although the pathways used by the organisms to reach the inner ear are not altogether clear, several routes have been suggested. These include the bloodstream, the auditory nerve, and the fluid supply of the inner ear and the middle ear. The prevalence of severe-to-profound sensorineural hearing loss among patients with this disorder is about 10%. Another 16% will exhibit transient conductive hearing loss. Interestingly, some patients with sensorineural hearing loss will exhibit partial recovery, although such findings are rare.4 4 See Fred H. Bess and Larry E. Humes. Audiology. The Fundamentals. Williams &Wilkins, 1995; p. 188.
(5) Sensorineural Hearing Loss Caused by Ototoxic Drugs.
A negative side effect of some antibiotic drugs is the production of the severe high-frequency sensorineural hearing loss. A group of antibiotics known as aminoglycosides are particularly hazardous. This group, also commonly referred to as the “mycin” drugs, includes streptomycin, neomycin, kanamicin, and gentamicin. A variety of factors can determine whether hearing loss is produced in a specific patient. These factors include the drug dosage, the susceptibility of the patient, and the simultaneous or previous use of other ototoxic agents.
Ototoxic antibiotics reach the inner ear through the bloodstream. The resulting damage is greater in the base of the cochlear. Outer hair cells are typically the primary targets, with only limited damage appearing in other cochlear structures. This results in an audiometric pattern of moderate-to-severe high-frequency sensorineural hearing loss in both ears.
Some ototoxic drugs cause a temporary or reversible hearing loss. Perhaps the most common such substance is aspirin. When taken in large amounts, aspirin can produce a mild-to-moderate temporary sensorineural hearing loss.
(6) Sensorineural Hearing Loss Due to Usher Syndrome.
Usher syndrome type 1 (USH-1) is an autosomal recessive disease characterized by profound hearing impairment, absent vestibular function, and progressive loss of vision due to retinitis pigmentosa.
Owing to the severe handicap of the combined disorders, early diagnosis of USH-1 is of crucial importance. The profound hearing deficit is often detected during hearing tests in infancy. The sight problems, however, do not develop until later and diagnosis is often delayed.
The diagnosis of Usher syndrome is established by electroretinography (ERG), as a confirmation of the retinitis pigmentosa is a prerequisite.5 5 K. W. Wright. Pediatric Ophthalmology for Pediatricians. Williams &Wilkins, pp 105-106.
(7) Sensorineural Hearing Loss Caused by Craniocerebral Trauma with a Fracture of the Base of the Skull and the Pyramid of the Temporal Bone.
The origin of otoneurological symptoms in this kind of trauma is very complicated, varied and multifold at different stages of the disease.
The disorders may be caused by different factors, such as by the peripheral damage to auditory and vestibular analyzers, central nervous system damage in the acute period of trauma (cortical damage, edema of the medullary substance and arachnoid membrane, minor hemorrhages especially in the vestibular section of CN VIII, etc.
In the case of craniocerebral trauma, the fracture lines from the calvarium go down to the skull base and damage the superior and posterolateral parts of the external auditory canal, middle, and inner ear.
In the case of longitudinal pyramidal fractures, bleeding from the ear may occur as a result of the rupture of the tympanic membrane and the skin of the external auditory canal. Very often patients with a longitudinal fracture develop neuropathy of the facial nerve on the side of the injury. Audiometry reveals partial loss of bone-conducting and air conducting hearing of high frequency tones (4000 to 8000 Hz).
In the case of transverse fractures of the temporal bone, which are produced by blows to the occiput, the fracture line begins in the posterior fossa at or near the foramen magnum and crosses the petrous ridge through the internal auditory canal or the optic capsule.
In the cases of transverse fractures of the temporal bone, due to automobile accidents or other causes of head injury, the labyrinth is involved more frequently than in longitudinal fractures. Severe vertigo with severe or total hearing loss is not uncommon in such injuries. In milder injuries, labyrinthine concussion may occur, with transitory auditory-vestibular symptoms. Audiometric investigation of the affected side in the acute period reveals hearing loss of a mixed type with the disturbances of both sound conducting and sound perception.
(8) Sensorineural Hearing Loss Caused by Neurinomas.
Cerebellopontine angle is a triangular area located at the junction of the cerebellum, pons and medulla.
Tumors of the cerebellopontine angle are mostly neurinomas of CN VIII, which develop from undifferentiated germinal Schwann cells, cochlear or more often vestibular nerves, situated in the inner acoustic duct. They squeeze the inner auditory artery and its branches, which produces ischemia of the inner ear and causes vestibular and hearing disorders. The tumor is normally located in one side, rarely in both sides. Most frequently occurring tumors are benign growths in the auditory nerve, referred to as acoustic neurinomas, acoustic shwannomas, acoustic neurilemoma.
The symptoms are caused by the compression or displacement of the cranial nerves, the brain stem, and the cerebellum. Trifacial (CN V) and facial nerves (CN VII) are affected most often because of their anatomical proximity to the vestibulocochlear nerve.
In research, applicant observed the development of neurinoma in patients during the period from 2 to 8 years. In the first stage, patients complained of tinnitus. In case of bilateral process the noise occurred in both ears. Then a gradual hearing loss from moderate to severe to profound was observed. In two patients, where neurinomas developed slowly, the appearance of tinnitus was not observed.
The first symptoms of neurinoma also include headaches and facial neuralgia. In the early stages, spontaneous nystagmus in the affected side maybe manifested, which is indicative of a vestibular disorder. In the case of neurinoma high frequency (2000-10 000 Hz) hearing loss is observed.
Considerable tumors cause hypertensive hydrocephalic syndrome, which can result in the loss of taste.
(9) Minimal Hearing Loss.
This is an insignificant loss of the peripheral hearing by 15-25 dB, which causes disorders of phonemic hearing. Phonemes are the basic elements of speech. The basic sounds can be analyzed as combinations of frequency-time relations. For example, a continuous component at 1000 Hz accompanied by a second component starting at 5000 Hz and descending rapidly to 500 Hz. A failure to differentiate phonemes leads to speech defects.6 6 See J. G. Nichollis, A. R. Martin, B. G. Wallace, P. A. Fuchs. From Neuron to Brain. Sinaur Associates, Inc. −4th ed., 2001, p. 375.
There are two types of peripheral hearing loss, including bilateral or unilateral. In cases of bilateral hearing disorders, even decrease loudness in the perception of different acoustic signals is observed (i.e, phonemes, speech, music, sounds of nature).
In the case of unilateral hearing disorders, the hearing perception decreases two times compared to normal perception. Unilateral hearing loss leads to the disorders of differentiation in the sound direction and the sound localization resulting in spatial hearing disorders.
Minimal hearing disorders can be caused by infectious and viral diseases of the mother, toxicosis of pregnancy, postnatal asphyxia, intracranial birth injury, hyperbilirubinemia, hemolytic disease of newborn; prematurity (birth weight below 3.3 lb), the use of ototoxic medications by the mother during pregnancy, and genetic factors.
Minimal hearing loss in the postnatal period can arise from trauma or infections of the inner ear and the trunk of the vestibulocochlear nerve. Inflammation of the internal ear is a result of the transition of the inflammatory process from the internal ear to the arachnoid membrane (in case of meningitis and encephalitis). Also, the dissemination of the infection by the blood in the case of infectious diseases, such as mumps, measles, scarlet fever, flu, and herpes.
A frequent cause of minimal hearing loss in most children with speech pathology is a result of overgrowth of adenoid vegetations (II and III degree), old otitis, tubootitis, obturation of the auditory duct caused by the chronic inflammation of its walls due to infections or purulent discharge from the middle ear, obturation of the auditory duct by earwax, and allergic rhinitis resulting in eustachitis.
In the case of sound conducting organs disorders, i.e., damage to the auditory duct to the tympanic membrane, a child has difficulty in the perception of such sounds as buzzing, knocking, low voice, and also low frequency and medium frequency phonemes. This results in speech impediment. Such disorders hamper the acquisition language.
Sound perception disorders (first degree sensorineural hearing loss) are caused by dysfunctions of the peripheral perceiving part of the auditory analyzer (part of the labyrinth with the Organ of Corty and the vestibulocochlear nerve endings).
In the case of minimal disorders of sound perception, the ability to hear high frequency sounds (buzzing, creaking, rustling, and high frequency phonemes) is diminished. High voice registers are not perceived as well as low frequency registers, especially in a noisy environment. The perception of phonemes, words, and speech is impaired.
Combined disturbances are a result of a combination of defects of the sound conducting and the sound perception. In such cases, the perception of high frequency and low frequency phonemes is impaired.
(10) Sensorineural Hearing Loss of Vascular Genesis.
Transitory ischemic attacks or an ischemic stroke in the vertebrobasilar system are often accompanied by dizziness and ataxia. In the case of occlusion of the inner auditory artery, patients complain of central dizziness with a unilateral loss of hearing, since this artery supplies the vestibulocochlear nerve (CN VIII). The inner auditory artery can move away from the basilar artery or from the anterior inferior cerebellum artery.
Dizziness is accompanied with nistagmus, the rapid phase of which is contralateral to the affected side. Hearing loss is of the unilateral sensorineural type.
Hearing disorders can be linked to atheromatose and atherosclerotic damage to the inner auditory artery, which causes blood supply disturbance in the organ of Corty, semicircular ducts, statoconic apparatus, and secondary degenerative changes in the nerve roots of the vestibulocochlear nerve.
These changes are characterized by simultaneous occurrence of headaches and tinnitus, frequently in the morning. These symptoms are observed in patients over 50 years of age.
Isolated loss of low frequency sound perception can testify to the vascular genesis of the hearing loss, as the blood supply of the base and the apex of the cochlear is carried out by different arteries. The more frequent reason for sudden deafness is vascular ischemia of the inner ear. Hearing loss can be observed on the side of cerebral symptoms of the cervical osteochondrosis. The main symptom is diminished sound perception with the prevailing progressive hearing loss. Audiographically, the lessening of hearing is observed on the side of the cerebral symptoms of the cervical osteochondrosis.